1. Field of Invention
The invention relates to saving data and avoiding data corruption in flash memory systems following a power failure and, in particular, to a system and method to actively isolate the flash memory system from a host system and employ an energy storage bank to facilitate storing data to flash memory following the power failure.
2. Description of Related Art
Solid state storage devices, such as Dynamic Random Access Memory (DRAM) and Static Random Access Memory (SRAM), have fast access times, require low power, and are generally more durable and compact than magnetic disk drives, but are also more expensive and are volatile, requiring constant power to maintain their memory. As a result, DRAM and SRAM devices are often utilized in electronic systems as temporary memory in addition to non-volatile storage media.
Another type of solid state storage device is a Flash EEPROM device (hereinafter referred to as flash memory). Unlike DRAM and SRAM devices, flash memory systems are non-volatile and retain their memory in the absence of a power source. However, flash memory shares the low power, compactness, and lack of moving parts advantages of solid-state memory and, for this reason, for many applications, flash memory systems are a desirable alternative to conventional magnetic disk drives.
Current flash memory systems typically comprise a processor-based system controller, a data buffer, and an array of flash memory chips especially designed for such a system. The flash memory system typically communicates with and receives system power from a host electronic device, such as a computer, digital camera, etc. An interface bus provides a data conduit between the host and the flash system. The controller directs read and write operations between the flash memory devices and the buffer.
One concern with flash memory systems is that writing data to the flash memory takes some time and it is desirable that, in case of a power failure, incoming data be successfully written to the non-volatile flash memory before the data is lost. One particular hurdle to be overcome is that in case of a power failure other circuit elements, including the host device, can drain power that would otherwise be available to flush the volatile RAM to the non-volatile flash memory. It is also advisable to terminate new incoming data from the host as this data can be readily corrupted by the power failure and it is preferred to not store potentially corrupted data.